Which 64-bit OS, John? I'm using Win7, which has not been out that long. XP and Linux here is all 32-bit.
Right now I am running Vista and Win7 64 bit. Actually I kinda prefer Vista 64 bit over Win7 64bit. I have a few free upgrade from Vista to WIN7 32 bit I need to do here sometime. My 64 bit Vista machine has a quad core Intel CPU and 8 gig of ram and it is a very stable machine and very quick. It can rip a video and play a high level game at same time. Vista 64 bit does not more than 4 gig to really run though while Win7 64bit does do better on 4gig than Vista. My ham computer though is a old XP laptop with a new HD and 1.5 gig of ram and a 1.7 gig Celeron 390. I have a quad core replacement machine I am building that I plan to run Vista 64 on.